Voltage regulator

1. A voltage regulator, comprising: an output transistor; a voltage dividing circuit for dividing an output voltage output from the output transistor to an output terminal, the voltage dividing circuit includes two or more switch circuits for switching in two or more resistors; an amplifier for comparing a divided voltage output from the voltage dividing circuit and a reference voltage so that the output voltage becomes constant; a drooping type overcurrent protection circuit; a fold-back type overcurrent protection circuit configured to lower an output current of the voltage regulator when the output voltage falls below a threshold voltage, wherein the fold-back type overcurrent protection circuit comprises: a sense transistor having a gate terminal connected to an output of the amplifier; a variable resistor circuit having one terminal connected to a drain of the sense transistor, the variable resistor circuit includes two or more switch circuits for switching in two or more resistors of the variable resistor circuit; and a control section for controlling a gate of the output transistor in accordance with a voltage generated in the variable resistor circuit; and a trimming signal generation circuit configured to selectively output a trimming signal, responsive to an input signal, to simultaneously switch in one or more of the two or more switch circuits of the voltage divider circuit and one or more of the two or more switch circuits of the variable resistor circuitry of the fold-back type over current protection circuit to simultaneously increase the output voltage and the threshold voltage of the fold-back type overcurrent protection circuit or simultaneously decrease the output voltage and the threshold voltage of the fold-back type overcurrent protection circuit.

2. A voltage regulator according to claims 1 , further comprising a non-volatile storage device for storing trimming data input to the trimming signal generation circuit.

3. A voltage regulator comprising: an output transistor; a voltage dividing circuit for dividing an output voltage output from the output transistor to an output terminal, the voltage dividing circuit includes two or more switch circuits for switching in two or more resistors; an amplifier for comparing a divided voltage output from the voltage dividing circuit and a reference voltage so that the output voltage becomes constant; a drooping type overcurrent protection circuit; a fold-back type overcurrent protection circuit configured to lower an output current of the voltage regulator when the output voltage falls below a threshold voltage, wherein the fold-back type overcurrent protection circuit comprises: a sense transistor having a gate terminal connected to an output of the amplifier; a variable resistor circuit having one terminal connected to a drain of the sense transistor, the variable resistor circuit includes two or more switch circuits for switching in two or more resistors of the variable resistor circuit; and a control section for controlling a gate of the output transistor in accordance with a difference between a voltage generated in the variable resistor circuit and the divided voltage; and a trimming signal generation circuit, responsive to an input signal, configured to selectively output a trimming signal to simultaneously switch in one or more of the two or more switch circuits of the voltage divider circuit and one or more of the two or more switch circuits of the variable resistor circuitry of the fold-back type over current protection circuit to thereby simultaneously increase the output voltage and the threshold voltage of the fold-back type overcurrent protection circuit or simultaneously decrease the output voltage and the threshold voltage of the fold-back type overcurrent protection circuit.

4. A voltage regulator according to claim 3 , wherein the fold-back type overcurrent protection circuit comprises an amplifier for detecting the difference between the voltage generated in the variable resistor circuit and the divided voltage.

5. A voltage regulator comprising: an output transistor; a voltage dividing circuit for dividing an output voltage output from the output transistor to an output terminal, the voltage dividing circuit includes two or more switch circuits for switching in two or more resistors; an amplifier for comparing a divided voltage output from the voltage dividing circuit and a reference voltage so that the output voltage becomes constant; a drooping type overcurrent protection circuit; a fold-back type overcurrent protection circuit configured to lower an output current of the voltage regulator when the output voltage falls below a threshold voltage wherein the fold-back type overcurrent protection circuit comprises: a sense transistor having a gate terminal connected to an output of the amplifier; a second transistor having a drain connected to a drain of the sense transistor; a first variable resistor circuit having one terminal connected to a source of the second transistor, the first variable resistor circuit includes two or more switch circuits for switching in two or more resistors of the first variable resistor circuit; a first amplifier for controlling a gate of the second transistor in accordance with a difference between a voltage generated in the first variable resistor circuit and the divided voltage; a second variable resistor circuit having one terminal connected to the drain of the sense transistor, the second variable resistor circuit includes two or more switch circuits for switching in two or more resistors of the second variable resistor circuit; and a second amplifier for controlling a gate of the output transistor in accordance with a difference between a voltage generated in the second variable resistor circuit and the reference voltage; and a trimming signal generation circuit, responsive to an input signal, configured to selectively output a trimming signal to simultaneously switch in one or more of the two or more switch circuits of the voltage divider circuit, and one or more of the two or more switch circuits of the first variable resistor circuit and one or more of the two or more switch circuits of the second variable resistor circuit of the fold-back type over current protection circuit to thereby simultaneously increase the output voltage and the threshold voltage of the fold-back type overcurrent protection circuit or simultaneously decrease the output voltage and the threshold voltage of the fold-back type overcurrent protection circuit.